Re: Moving forward...
Talislanta has a bit different spin on "undead" than a lot of other games; each type is more or less individualized, so how spells would affect them would depend a lot on that type. For instance, Talislanta doesn't have zombies on its own in the sense of the zombies we've seen.
As far as illusion goes, Tal illusion magic is odd in that it may not influence the mind per se, but actually be a physical manifestation. For example, to cast a "light" spell in Tal, you'd use the illusion mode, which creates a "real" light you can see by.
Bottom line, though, it's going to depend upon what your character knows of both illusion magic and of zombies. For instance, they might see an illusionary bunch of people running away from them, but, for all we know, they are more attracted by smell or sound than sight. *shrug*.